A bone scan (Nuclear Medicine Bone Scintigraphy) is a specialized medical imaging test that provides a functional map of the skeleton. Unlike an X-ray or DEXA scan, this procedure looks for changes in bone metabolism. It uses a small, safe amount of a radioactive material, known as a radiotracer, introduced into the bloodstream. This tracer collects in areas where bone is actively building or breaking down, allowing physicians to detect disease processes not yet visible on other imaging tests.
Accessing and Scheduling the Test
A bone scan requires a referral from a healthcare provider, such as a primary care physician, oncologist, or orthopedist. The physician determines the medical necessity and provides the order to the imaging facility, where the scan will be scheduled. These tests are primarily conducted within the Nuclear Medicine departments of hospitals or at dedicated outpatient imaging centers. Appointments often require advance booking because the radiotracer, typically Technetium-99m MDP, has a short half-life of only six hours. This means the tracer must be prepared fresh for each appointment, necessitating careful scheduling.
The Procedure Step-by-Step
Preparation for the bone scan is minimal, requiring no fasting or changes to diet or medication. Patients should wear comfortable clothing without metal fasteners and remove jewelry or any metallic objects that could interfere with the imaging equipment. Upon arrival, the technologist will confirm your identity and explain the procedure before beginning the first phase.
The procedure begins with the injection phase, where the radiotracer, Technetium-99m MDP, is administered intravenously into a vein in the arm or hand, similar to a routine blood draw. The substance causes no physical sensation. The MDP component is a phosphate compound that binds to the hydroxyapatite crystals in the bone, while the Technetium-99m allows the tracer to be detected by the imaging camera.
Following the injection, there is a necessary waiting period that typically lasts between two and four hours. This delay is required for the tracer to successfully circulate and be absorbed by the bone tissue in areas of active metabolism. Patients are often encouraged to leave the department and move around during this time, provided they return at the scheduled time.
Hydration is an important component of the waiting period. Patients will be instructed to drink several glasses of water or other fluids, totaling 32 ounces or more. Increased fluid intake helps the body clear any unbound radiotracer circulating in the soft tissues and the bladder. This clearance reduces background radiation and prevents the tracer concentrated in the bladder from obscuring the view of the pelvic bones during imaging.
When the waiting period is complete, you will be asked to empty your bladder before moving to the imaging room. The imaging phase uses a specialized device called a Gamma camera, which detects the gamma rays emitted by the Technetium-99m tracer concentrated in your bones. You will lie on a padded table while the camera moves slowly above and beneath your body to capture images of your entire skeleton.
The imaging portion typically takes between 30 and 90 minutes, depending on the area being examined. Patients must remain completely still during this time to prevent motion blur, which compromises image quality. The Gamma camera does not produce the loud noise associated with MRI machines, nor does it enclose the patient like a CT scanner, but it may move very close to the body without touching.
Interpreting Results and Post-Scan Safety
Once imaging is complete, the resulting pictures are analyzed by a Nuclear Medicine physician or a radiologist specializing in these functional studies. These experts look for areas of increased radiotracer uptake, known as “hot spots,” which indicate high metabolic activity in the bone. Hot spots can signal conditions such as fractures, infection (osteomyelitis), arthritis, or the presence of tumors.
Conversely, areas of decreased or absent uptake, called “cold spots,” can also indicate pathology, such as avascular necrosis or certain types of tumors. The physician integrates the imaging data with your clinical history to generate a comprehensive report. This report is sent to your referring physician, who will review the findings and discuss them with you, usually within a few days.
Immediately following the procedure, the amount of radiation exposure from the radiotracer is low, comparable to a standard diagnostic CT scan. The radioactive material exits the body naturally, primarily through urine and feces, with the majority eliminated within the first 24 hours. Patients should continue to drink extra fluids for a full day after the test to expedite this clearance process.
As a precaution, it is recommended to minimize prolonged close contact with pregnant women, infants, and young children for the first 24 hours after the scan. Patients can otherwise resume all normal activities, including work, driving, and exercise, immediately after leaving the facility.